At roughly the same time every year, the world’s oldest military alliance assembles in Brussels to reaffirm its unity, strength, and resolve. The annual North Atlantic Treaty Organization (NATO) meetings are typically an opportunity for member states to take stock of the most pressing international security issues of the day. The event is largely a highly choreographed and antiseptic affair; after two days of conversation, speeches espousing the indispensability of the rules-based world order, and the crafting of a lengthy but bland joint communique, the delegations get on their planes and fly back home.

Needless to say, President Trump has shaken that routine. In more conventional times, European heads-of-state and NATO officials would be eagerly awaiting the transatlantic reunion rather than biting their nails in nervous anticipation and wondering what the U.S. president may say or do during the summit. But, alas, Trump—a man who once called NATO an “obsolete” relic of the Cold War and who takes joy at scolding Washington’s European partners for lackluster military spending—is the human antonym for conventionality. Trump’s aggressive posture towards traditional western institutions in general, from the European Union to the G-7 forum, is no doubt causing consternation among European leaders who have taken America’s fealty to the transatlantic relationship for granted.

Trump, of course, has since amended his description of NATO as obsolete. It is, after all, still an operational military alliance that continues to send troops to Afghanistan, an active war zone not getting any less violent. Yet it would be highly unwise for members of the alliance to discount what Trump has to say. While NATO is not at risk of extinction, it finds itself at a critical inflection point in its nearly 70-year history. Continuing with a business-as-usual is not an option.

The most immediate problem within the alliance is the spending disparity between the United States and everybody else. Granted, it would be foolish to expect Germany, Spain, Italy, and France to invest as much money in real terms as the U.S. to national defense (the U.S., after all, is an $18.5 trillion economy). Yet it is hardly unreasonable to expect all of NATO’s members to fulfill their financial commitments toward NATO’s collective defense. While non-American financial contributions have slowly risen over since 2015, it’s nowhere near close to meeting their obligations, and burden sharing continues to be a significant impediment to a capable, adaptive, mobile, and fully prepared military alliance.

The latest figures from NATO headquarters underscore a trend that is not only grossly unfair to the American taxpayer, but unsustainable from the standpoint of alliance unity. At the end of this year, NATO Secretary General Jens Stoltenberg assesses that eight of NATO’s 29 members (including the U.S.) spend at least 2 percent of their GDP on national defense. The 2 percent guideline is arbitrary, but one the entire alliance nevertheless committed itself to upholding during a previous summit in Wales. Of the $945.6 billion NATO countries expended on their militaries, Washington’s portion was an astronomical $703.7 billion. In other words, 74 percent of NATO’s entire defense expenditure in 2017 was underwritten by the U.S., a nation whose national debt just exceeded $21 trillion this past March for the first time. For Trump to ignore such lopsided numbers and fail to forcefully press the point during next month’s summit in Brussels simply a dereliction of duty and feckless presidential leadership.

As important as the burden-sharing issue is, there is an even more immediate imperative NATO members are confronting: what exactly is the alliance’s raison d'être in a world that is far more frenetic, multidimensional, and in many ways more complicated than when the organization was established in 1949?

During the Cold War, NATO’s mission statement was clear and unequivocal: preserve, protect, and defend the democracies of Western Europe from a Soviet invasion and ensure that any Soviet division bursting through the Fulda Gap would spur the entire alliance into action. While counteracting the Soviet Union would inevitably be a bloody affair, at least NATO’s members understood who their primary adversary was.

The Soviet Union’s dissolution, however, removed the foundation that upheld NATO’s structure practically overnight. Ever since, the alliance has been a beast in search of a mission. The collapse of a bipolar world made way for the emergence of a vastly different global landscape that NATO’s founders did not imagine at the time. Twenty-six years later, an organization originally created to hold the line against a peer competitor has transitioned into a security collective in search of challenges to fix and whose membership continues to expand.

Today, NATO is an overstretched alliance conducting missions as diverse as training Iraqi counterterrorism forces to rescuing stranded migrants in the Mediterranean Sea. The mission sets have gotten so unwieldy that NATO members find themselves increasingly divided about which national security issue—Russia, migration, terrorism, or cyber security—deserves the most attention. One will get a different answer depending on which government is asked.

Can NATO find a necessary, appropriate mission for today’s world? Just as important, can NATO even survive if the whole alliance remains totally dependent on the money, military capacity, generosity, and good will of a single member—the United States?

These are existential questions for NATO. The debate is certain to be stressful and it could very well cause further strain in relations with Washington on one side and its European allies on the other. Indeed, finding answers will take much longer than a short two-day summit.

But the transatlantic community can not afford to avoid the tough discussion any longer. The sooner this very tough family conversation begins, the better off it will be.

Daniel DePetris is a fellow at Defense Priorities.

This piece was originally published by CNBC.com on July 3, 2018. Read more HERE.